Originally Posted by
stilton
Curious to know what happens when there isn’t enough ‘puff’ to start two engines simultaneously in that scenario
Will the auto start / FADEC abandon the start(s) if adequate rotation is not achieved within a specific time period, close to starter duty cycle limits ?
Assuming it would not allow fuel on in this circumstance ?
That's basically correct - the autostart measures how long it takes of N2 (or N3) to accelerate - if it's too slow it aborts and puts up the ENG X AUTOSTART message on EICAS (and sets a CMC message as to the cause).
Apparently that's happened during single engine starts on the Large Cargo Freighter 747-400 (aka the Dream Lifter). As part of the mod, they removed the APU (running the fuel and pneumatic lines through where the fuselage swings open would have been problematic) so they need a ground cart. Turns out not all ground carts are up to the task...